1. Field of the Invention
The invention relates to an improved MOSFET device structure and the method of forming the device structure. A polysilicon spacer is formed on the gate electrode forming a gate structure with a cavity. The channel implantation is self aligned through the cavity. A fully overlapped Light-Doped-Drain structure is used to improve device characteristics. Deep boron implants are used to improve punch through voltage.
2. Description of the Related Art
In using field effect transistors in the formation of integrated circuits increased density and increased performance has long been recognized as having key importance. When channel lengths in N-channel Metal Oxide Semiconductor Field Effect Transistors, NMOS, become very small, less than about 2 microns, hot-carrier effects can degrade device performance. To improve device performance for short channel devices a Lightly-Doped Drain, LDD, structure is often used to control these hot-carrier effects. In additional punch through can degrade device performance in Metal Oxide Semiconductor Field Effect Transistors when channel lengths become small. In addition it is important to maintain high reliability and good device characteristics for submicron applications.
This invention uses self aligning methods to form the critical regions in the device. A fully overlapped Light-Doped-Drain is used to improve device characteristics for submicron devices. A deep boron implant, which is self aligned, is used to improve punch through voltage for short channel devices.